1. Field of the Invention
The present invention relates generally to satellite image fusion method and system. More particularly, the present invention relates to the satellite image fusion method and system for fusing panchromatic image data of a high resolution and multispectral image data of a low resolution using an IHS fusion method.
2. Description of the Related Art
An earth observation technology can play a very important role in a resource exploration and an environment monitoring and management which closely relate to human existence, and is attracting much attention not only for the present but also for the future. The earth observation is carried out by fusing various satellite images. For doing so, it is necessary to enhance a spatial resolution of the images by fusing the images having different spatial resolutions and different spectral resolutions.
Particularly, a panchromatic (black-and-white) optical image which images a spectral reflection energy of a wavelength range of visible light has a high resolution. By contrast, a multispectral image which collects data by segmenting wavelength range from the visible light band to the infrared ray and thermal ray bands per unit wavelength range, disadvantageously degrades the spatial resolution.
In this respect, various methods for fusing the high-resolution panchromatic image and the low-resolution multispectral image have been steadily developed. For example, such various methods include Intensity-Hue-Saturation (IHS), Principle Components Analysis (PCA), arithmetic combinations, wavelets-based fusion, and so on. Particularly, the IHS fusion method is the most recently generalized image fusion scheme. It is known that the IHS is quite suitable for the fusion of the large-capacity high-resolution satellite images. However, the IHS fusion method distorts color information of the multispectral image in fusing process because of a pixel value difference between the panchromatic image and the intensity image. Researches are conducted on diverse methods for fusing the spatial information of the high resolution of the panchromatic image while minimizing the distortion of the color information of the multispectral image.
In the recent paper by Tu et al. titled “A fast intensity-hue-saturation fusion technique with spectral adjustment for IKONOS imagery”, IEEE GRSL, vol. 1, no. 4, pp. 309-312 (2004), the distortion of the color information is mitigated by substituting the bands of the multispectral image into Equation 1 which enhances the IHS fusion method.
                    I        =                              (                          R              +                              0.75                ×                G                            +                              0.25                ×                B                            +              N                        )                    3                                    [                  Equation          ⁢                                          ⁢          1                ]            
In Equation 1, I denotes a pixel value included to the intensity image, and R, G, B, and N denote a Red band component value, a Green band component value, a Blue band component value, and a Near Infrared band component value of the pixel in the multispectral image respectively.
But, Equation 1 acquires two coefficients of 0.75 and 0.25 which are the coefficients of G and B, using the relatively small number (=92) of the IKONOS images. Thus, when all of the IKONOS images are collectively applied to Equation 1, it is difficult to obtain the optimized Intensity (I) value.
In addition, since Equation 1 targets only the IKONOS image, it is hard to apply Equation 1 to other satellite images such as Landset images and SPOT images.